Korbinian Schraml

Multi-layer patch antenna array design for Ka-band satellite communication

The GeReLEO-SMART project aims to build a communication experiment to be launched on the German technology demonstration mission “Heinrich-Hertz” (H2SAT). On its geostationary orbit it will demonstrate new space appropriate technology of a 26 GHz patch antenna array with integrated low noise amplifiers (LNA), MEMS switching of the RF signal and FPGA mission control. The antenna consists of a multi-layer structure including a pre selector band pass filter to suppress other radio sources on the Heinrich-Hertz satellite. The reception antenna consists of five 2×2 array of circular patch antennas with a feeding network. A temperature stabilized LNA is buried into the PCB stack to minimize transmission line losses in front of it. Two different designs of the antenna array are presented to compare the space qualification by real tests and measurements.

Side-lobe reduction of horn antenna using circular patch mushroom-like EBG structure

This paper proposes a reconfigured horn antenna with reduced side-lobe radiation by using electromagnetic band gap (EBG) structure. A mushroom-like structure with a circular-shaped patch as unit cell is designed to achieve a complete EBG. The EBG structure is lined on the metal wall along the E-plane of the horn antenna. This causes the surface waves on the metal wall to be suppressed, resulting in lower side-lobe emission. A conducting wedge is inserted on the gap between the EBG structure and waveguide feed aperture to achieve impedance matching in the antenna. In addition, the proposed horn antenna is suitable for high power systems due to a purely metallic construction of the EBG structure.

Concept for low cost CNC machined gain reference antennas

Gain standards for accurate antenna measurements are expensive due to their extensive calibration procedure. This paper presents a concept for low cost antennas that comprise of sheets of FR-4 which are accurately manufactured using modern CNC technology. This accuracy in turn will render the calibration procedures unnecessary. The impact of tolerances is studied to determine whether the concept is eligible for further investigation.

Comparison of meander line and NFRP miniaturization techniques for RFID on-chip antennas

Antenna miniaturization techniques using meander line and Near-field Resonant Parasitic (NFRP) are presented in this paper. Also, antenna performance including reflection loss and gain have been optimized during the scale-down process. The proposed antennas are compared with the theoretical limits of small antennas to confirm the optimized performance in a limited space. The smallest possible size of the proposed antenna is 0.0232λ0 in length or ka = 0.103. The proposed scaling strategy will be applied to the design of RFID on-chip antennas in the future.

Enhanced physical layer security using monopulse antennas

The paper proposes a new method for private point-to-point communication. It employs a monopulse antenna system, where the summary beam is used to transmit the useful signal to the intended receiver, while the differential beam is used to generate noise, in order to bury the signal for angles other than boresight. The method is tested using simulated QPSK modulation, providing a beamwidth with bit error rate below 10-4 within ±6°, while raising BER steep to 0.5 at 32°.

Far field analysis of wrinkles in space membrane antennas

Large deployable antennas (LDA) are an upcoming technique used as space borne reflector antennas. Low stow volume and mass are one of the key advantages allowing big reflector diameters to be launched on conventional vehicles. A primary concern in reflector antenna building is surface accuracy, especially at high operating frequencies. Conventional LDA use sophisticated high cost mechanics to deploy a mesh structure with low surface error. But deployable structures are also used as a drag sail to deorbit satellites when their life time is exceeded. The surface structure of such a drag sail is of subordinate interest, leading to low cost deployment mechanics, which are easy to build. The idea described in this paper is to use the drag sail deployment technique and use the expanded membrane surface as a reflector antenna. The effects of the surface errors, which are inevitably introduced by the mechanics, are studied to help to determine a break-even point between antenna performance loss and cost reduction compared to a conventional LDA. Possible applications are small satellites like CubeSats, which could enhance their communication link budget by deploying a medium performance but low cost LDA.

Lightweight and cost efficient spaceborn patch antenna

In order to achieve lightweight yet low cost antennas for use in a geostationary space environment, the GeReLEO-SMART project develops a substrate-based, multilayer antenna structure which can replace traditional horn antennas as feeds for reflector antennas. To verify a design, an example mission is developed, consisting of a 2×2 patch antenna array with an integrated stripline bandpass filter. The operation frequency is 25.935 GHz. This multilayer antenna will be tested on board of the German technology demonstration mission “Heinrich-Hertz” (H2SAT). The design passed all tests for space qualification without decrease in performance.

Estimation of the propagation constant in multilayer microwave circuits using a low cost multiline system

For microwave circuits and planar antennas, complex multilayer structures pose a challenge for the designer since different materials for substrates, bonding films and coating have different frequency behaviour. Furthermore, the traditional measurement techniques for the complex permittivity rely on different field distributions than those of a transmission line making it hard to account for non-isotropic materials. This paper presents a method of measuring complex propagation constant γr, eff and the effective permittivity ϵr, eff with low cost set of simple transmission lines. It uses parts of the Multiline Calibration Technique which was developed for the calibration of vector network analyzers. An implementation in MATLAB as well as a study on the performance of the algorithm using simulated lines with added noise are presented.